FIGURE 1. PP1 is the catalytic subunit of merlin phosphatase.

a, Immunoprecipitated C-merlin was incubated with or without calf intestinal phosphatase (CIP), resolved by SDS–PAGE and detected by immunoblotting (C-18, merlin antibody). b, Immunoblots of C-merlin from cells growing at low cell density (LCD) or high cell density (HCD). c, Immunoblots of C-merlin from cells subjected to serum withdrawal (5 min) or incubation with hyaluronan (HA; 100 g ml^-1 for 5 min). d, Gel migration of mutant (S518A, S518D) C-merlin relative to that of the wild type (WT). e, f, Serum-withdrawal-induced dephosphorylation of C-merlin (e) and of full-length merlin probed with phospho-merlin-specific antibodies (f) is inhibited by pretreatment of cells with okadaic acid (OA). g, In vitro dephosphorylation of immunoprecipitated (IP) C-merlin by recombinant PP1 and PP2A. h, Immunoprecipitation (IP) of endogenous merlin (merlin antibody A-19 compared to an isotope control antibody iso). Co-precipitated proteins detected with pan PP1 and PP2A antibodies.